In recent years, there has been required a minute optical lens and an optical lens unit applicable to, for example, a small-sized device such as a mobile phone and an endoscope, which has an optical fiber or a solid-state imaging element such as CCD (Charge Coupled Device)-type image sensor and a CMOS (Complementary Metal Oxide Semiconductor)-type image sensor. In the assembling of this kind of small lens to a lens frame, it is sometimes difficult to secure an adhesion space because of a spatial limitation, and in this case, it is likely that adhesion peeling or the extrusion of an adhesive is generated.
For securing the adhesion space, there is known a technique of providing a tapered part for the outer circumference of a lens flange part along the optical axis direction (refer to patent literature 1). Furthermore, there is also known a technique of providing an adhesive reservoir portion in the lens frame in order to avoid the adhesion peeling or the extrusion of an adhesive (refer to patent literatures 2 and 3, for example).
However, under a situation in which smaller sizes of the optical lens and the optical lens unit are requested, the peripheral part located outside an optical surface of a lens such as the outer circumference of the flange part is not always sufficiently secured. In the case of, for example, FIG. 2 in the patent literature 1, when the tapered part is provided on the outer circumference of the lens, the adhesion space is secured by making a slope so as to form a shape in which the adhesive reservoir portion spreads as coming closer to a contact part provided for the alignment with the lens frame in the optical axis direction. In this case, the lateral distance between the lens frame and the contact part become small in the direction perpendicular to the optical axis compared with the case where the tapered part is not provided. Accordingly, when applying the shape as in patent literature 1 under the situation in which a smaller size is requested, it becomes difficult to secure a sufficiently large size for the contact part. When the contact part is not sufficiently secured, the adhesive having reached to the contact part from the adhesive reservoir portion might leak or extrude at the time of adhesion.
Furthermore, when the optical lens and the optical lens unit are requested to have smaller sizes, the size of the lens frame is also restricted, and it might become difficult to provide an adhesive reservoir portion having a deformed shape on the lens frame side or the like as in, for example, patent literatures 2 and 3, and to secure a sufficiently large adhesive reservoir portion.